Semiconductor dice are typically fabricated in wafer form. A silicon wafer undergoes a series of well known processing steps to fabricate a plurality of dice on the wafer. After fabrication, the individual dice are separated by cutting or sawing the wafer along the scribe lines. The individual dice are then usually encapsulated in a package. Common types of chip packages used in the semiconductor industry include, but are not limited to, dual in-line packages (DIPs), leadless lead frame packages, bumped die packages, ball grid array packages, etc.
Most, if not all semiconductor chips, regardless of their functionality, require some type of passive component, such as resistors, capacitors, inductors, or transformers, for proper operation. For example, analog and power linear power regulator chips will typically rely on some type of filter capacitors. The filter capacitors store charge which helps the power regulator maintain a steady voltage supply. Similarly, high speed digital circuits require highly regulated line voltages. To create the proper line voltage, sophisticated capacitor filter networks are used to provide the needed steady power supply for the digital circuitry to properly operate at the high clock frequencies. Accordingly, most chips rely on some sort of filter capacitor(s) to provide regulated line voltage for operation. Many integrated circuits rely on resistors for a whole host of reasons, such as pull up resistors, voltage dividers, etc. For example, battery powered devices using high speed digital circuits typically require several different voltages to be created from the battery. Very often switching voltage regulators/converters use inductors and/or capacitors as energy storage devices for the voltage levels.
Chip and system designers have developed several methods for providing both analog and digital circuitry with access to the needed passive components.
One known method is to fabricate the passive component directly on the die along with the other circuitry on the chip. For example, resistors and capacitors can be fabricated using thin films and dielectrics deposited or formed directly on the die. The problem with this technique, however, is that the size of the resistors and capacitors is limited. The die itself is typically small. Also a large portion of the surface area on the die is often dedicated to other circuitry. The resistive and capacitive values that can be achieved by fabricating resistors and capacitors on the die are therefore relatively small.
Another approach is to mount the passive element on a circuit board adjacent the chip. Electrical traces on the board connect the leads of the passive element to the appropriate pins or contacts on the chip. The issue with using external passive elements is that they occupy a large amount of surface area on the printed circuit board. This is particularly problematic with many small sized, high volume, consumer electronic devices, such as cell phones, MP3 players, personal digital assistants, etc. The addition of the external passive components on the boards places a constraint on how small these consumer devices can be made.
Yet another solution is to fabricate the passive components within the various layers of the printed circuit boards the chip is to be mounted on. For example, thin film resistors, dielectric layers, and the like, may be formed on the various layers of the printed circuit board to form the resistors and capacitors. Metal traces and vias are then used connect the passive component to the pins or contacts of the integrated circuit package mounted onto the board. The problem with this approach is that it is inefficient. Relatively large amounts of surface area on the printed circuit board are usually required to create the resistors, capacitors and inductors. Accordingly, forming the passive elements on printed circuit boards is problematic for many applications, such as cell phones, PDAs, MP3 players and other mobile or small devices where space is at a premium and the smaller the printed circuit board the better.
Since many chips require passive components with resistance, capacitance, and/or inductance values that are simply too large to be implemented either on chip or embedded within the layers of a printed circuit board, the only practical solution thus far has been to mount a separate passive components adjacent the chip onto the board.
The term “form factor” is generally used in the semiconductor industry to refer to passive components that are approximately the same size or slightly larger than the chips that use the passive components. In many applications, the chips and their requisite form factor passive components are mounted side by side on the board. As previously noted, this arrangement tends to occupy a great deal of space on the board, which can become problematic, particularly with small and/or portable consumer devices, such as cell phones, PDAs, MP3 players, and other small sized devices. Thus fitting a printed circuit board populated with semiconductor chip packages and their needed passive components into a small consumer device, such as an MP3 player or cell phone, has become a significant challenge.
An apparatus and method for making semiconductor packages having integrated circuits mounted onto passive electrical components is therefore needed.